Yet when it's schools withering, we're fine. Every year we pour $53 billion into a system that can only divide us, with a quarter of it – $12.7billion – going straight to educational big business.

And for what? What does it buy, this immense spend? It buys a system that deliberately tribalises children before they can read, that has parents selling their houses for school fees, stressing about homework and entry exams and increasingly investing in private tutoring for four-year-olds. Yet for all that effort and angst, it's a system that leaves us (as recent news yet again makes clear) less well educated with each passing year.

Increasingly, education seems like happiness: despite (or because of) a vast global industry devoted to generating angst, the harder we try, the more elusive it becomes.

Three arguments are usually advanced for private schools. One, choice. Parents should be free to choose expensive or religious education for their kids if they wish. Two, quality. Private schools offer better education and, regardless of politics, the kid's interests should prevail. Three, burden: private schools, far from siphoning wealth from the public system, lightens its load.

None of these arguments stack up. Take choice. Choice relies on comparison, product to product. But education is not shampoo. You can't try a school for a few weeks or years and know that how your kid tracks is a direct result, or how things might have been different elsewhere. So comparison is illusory.

Which goes directly to the quality argument. Many parents send their kids to private schools, even when they don't approve, because they think the education is better and there's at least a modicum of discipline. And yes, private schools are more able to impose order and sack teachers for non-performance. But, given that these students are already more biddable and more literate, it's impossible to prove any net educational benefit.

Three years ago, David Gillespie (author of Free Schools) argued persuasively that, once you correct for socioeconomic advantage, even the most expensive schools add nothing to educational outcome. This may be one reason why – it's now reported – more wealthy parents are choosing to put their kids in the public school system.

Across the board, though, quality is low and falling, with consistently dropping international test scores in maths and science. Even a recent and welcome improvement in reading, mainly because girls love books, still takes us only to about the Organisation for Economic Co-operation and Development average. Could do better.

And that leads immediately to the idea of burden. Does anyone suggest sport's Big Money dudes – the sponsors and gravy-trainers, the owners and big-bucks players – are taking the burden off the public sport system?

No, they're creaming off the talent, quarantining it from public access for vast private profit and getting a public leg-up on the way. This is so wrong on so many levels. What's weird is that we can see it with sport, but with schooling – where the bill is six times the size, and annual – we're blind.

But honestly – burden? According to the ABC, almost a quarter of the $53 billion funding of schools ($12.7 billion) goes to private schools – which educate roughly a third (34 per cent) of populace. So each private school student sucks almost two-thirds as much as each public one. Before the benefit of their $30,000 in fees.

In other words, for every private school student the burden decrement on the public system is fairly small, but the personal advantage is immense.

This is manifestly unfair. Private schools heighten inequality, privileging the privileged, hogging the teaching talent and siphoning off kids already equipped with reading backgrounds, so depriving the public system of beneficial peer-to-peer learning.

But that's not all. Tribalising children before they outgrow the booster seat can only encourage class-based and religious sectarianism. Friendly rivalry is one thing. But you can't allow a lovely school like Loreto Normanhurst without also allowing schools that demand your mother's birth certificate, or preach against infidels. This can only bring hatred.

But the best argument against private schools is productivity. Squabble all you like about divvying up the pie but far more useful – and more fun – is growing it. Technically, yes, education is a burden, but as an appreciating asset it's more house than car; an investment.

Forty years ago, Finland stunned the world by nationalising schools, revering teachers, ending streaming, entering school late, shrinking the school day, reducing homework and extending holidays – then topping every test. Lately, its schools slipped a little, mainly due to global financial crisis-driven reductions. But its schools are still up there, and in an extraordinary turn-up Dr Pasi Sahlberg, who as minister designed the Finnish system, will move to Sydney next year, to teach.

Maybe we can persuade him to fix our schools, putting all schools up there with Grammar, say, or Loreto. If he needs more than Gladys' stadium money, we could give him WestConnex as well. Wouldn't that be great? Save the parks, clean the air, grow the future. Win, win, win.